Typhoid fever is a common serious disease in many parts of the world. Purified capsular polysaccharide from Salmonella typhi (Vi) is used as a vaccine, providing about 70% protection against typhoid fever in individuals 5- to 45-years-old. However, the vaccine is unable to establish immunological memory and is ineffective in infants or toddlers [1]. A conjugate vaccine of Vi coupled to recombinant mutant Pseudomonas aeruginosa exoprotein A (Vi-rEPA) gave a booster response in young children and was highly efficacious [2].
It is an object of the invention to provide new processes for the production of Vi conjugate vaccines that may be employed on an industrial scale.